fixed documentation for docs-agent demo (google#183)

* fixed documentation for docs-agent demo

* Update README.md

Author: thesanju

demos/palm/python/docs-agent/README.md

@@ -603,6 +603,10 @@ To launch the Docs Agent chat app, do the following:
    already running on port 5000 on your host machine, you can use the `-p` flag to specify
    a different port (for example, `poetry run ./chatbot/launch.sh -p 5050`).
 
+   **Note**: If this `poetry run ./chatbot/launch.sh` command fails to run, check the `HOSTNAME` environment 
+   variable on your host machine (for example, `echo $HOSTNAME`). If this variable is unset, try setting it to 
+   `localhost` by running `export HOSTNAME=localhost`.
+
    Once the app starts running, this command prints output similar to the following:
 
    ```